Not applicable.
1. Field of the Invention
The present invention relates to devices and methods for surgical training, and in particular, to such devices and methods which are useful in training on microvascular and microsurgical procedures on both human and animals.
2. Brief Description of the Related Art
Laboratory training models are essential for developing and refining surgical skills, especially for microsurgery. The closer to live surgery the model is, the greater the benefit. At present, training is limited to artificial models that simulate human anatomy, anesthetized live animals and cadavers, but none of them reliably mimic the anatomy and the characteristics of the vascular tree and tissue in the human and animal anatomy during live surgery, in particular, hemorrhage. Training models using a portion of animal anatomy are known, but even with such a model, training is limited to a few procedures and cannot replicate the experience of xe2x80x9cskin-to-skinxe2x80x9d procedures, i.e., from opening to closing. Cadaver models injected with colored silicone, gelatin, or any other congealed material lack bleeding, pulsation and fluid vascular filling, which allow manipulation of the vessels, hemostasis, clipping, or suturing. On the other hand, live anesthetized animals do not represent true human anatomy, apart from the ethical considerations involved in the use of live animals in surgical training.
Microsurgery, and especially neurosurgery, demands the development of dexterity and skill for both basic and fine procedures and techniques. In particular, in organs such as the central nervous system or vascular system, the surgeon""s individual skills play a crucial role in determining the outcome. Hence, the emphasis has been on laboratory training in preparing people for the operating room experience. (Yasargil M G, Microneurosurgery, Microsurgical anatomy of the basal cistern and vessels of the brain. New York: Thieme Medical Publishers, 1984, Volume 1, p. vi). The fine manipulation and dissection of the vessels with anastomosis are usually practiced on live anesthetized animals or artificial models. (Yonekawa Y, Frick R, Roth P, Taub E, Imhof H-G: Laboratory Training in Microsurgical Techniques and Microvascular Anastomosis. Oper Tech Neurosurg 2:149-158, 1999.). Unfortunately, these are limited to simple techniques and have no relation to the actual anatomy or surgical crises that are encountered by the trainee in live surgery. A critical part of this training is mastering the anatomy.
To improve the illustrative value of cadaveric dissection, colored materials are injected into the vessels of cadavers to identify the arteries and veins for anatomical studies. Fluorescein and radiopaque substances, silicone, gelatin, latex, acrylic, or tinted polyester resin have been used for this purpose. (Gibo H, Carver C C, Rhoton A L Jr, Lenky C, Mitchell R J: Microsurgical anatomy of the middle cerebral artery; J Neurosurg 54:151-169, 1981; Sanan A, Abdel Azez K M, Janjua R M, van Loveren H R, Keller, J T: Colored silicone injection for use in neurosurgical dissection: anatomic technical note. Neurosurgery 45:1267-1274, 1999; Smith R, Rhoton A L Jr: Comment. Neurosurgery 45:1272-1273, 1999; Umansky F, Juarez S M, Dujovny M, Ausman J I, Diaz F G, Ray W J: Microsurgical anatomy of the proximal segments of the middle cerebral artery. J Neurosurg 61:458-467, 1984; Diaz J: Comment. Neurosurgery 45:1271-1272, 1999.).
Mechanical pressure pumps have been used to introduce and perfuse embalming fluids via the common carotid or femoral arteries (Coleman R, Kogan I: An improved low formaldehyde embalming fluid to preserve cadavers for anatomy teaching. J Anat 192:443-446, 1998; O""Sullivan E, Mitchell B S: An improved composition for embalming fluid to preserve cadavers for anatomy teaching in the United Kingdom. J Anat 182:295-297, 1993.). Mechanical pumps have also been used to introduce liquids into artificial training models or into portions of animal anatomy as described in U.S. Pat. No. 5,425,644 to Szinicz.
In studying the role of neurovascular compression in trigeminal neuralgia, Hamlyn described injection filling of cadaveric vessels to determine the neurovascular relationships in the posterior fossa (Hamlyn P J: Neurovascular relationship in the posterior fossa, with special reference to trigeminal neuralgia. 1. Review of the literature and development of a new method of vascular injection and filling. Clin Anat 10:371-379, 1997.).
Various attempts have been made to preserve living organs using various combinations of pumps, conduits and fluid reservoirs connected to the vascular system of the organ. See, for example, U.S. Pat. Nos. 4,666,425; 5,326,706; 5,494,822; and 3,892,628.
Training models with means to simulate the behavior of blood or other fluids in the human body are known from U.S. Pat. Nos. 6,234,804; 5,951,301; 5,634,797; 5,620,326; 5,320,537; 5,215,469; 4,773,865; 3,027,655; 4,182,054; 2,871,579; 2,752,697; and Published Patent Application U.S.2001/0019818A1. The disclosed devices employ simulations of living anatomy and are generally limited to one or a few procedures. While such models may be valuable in the early stages of training, they are less effective for higher level training in surgical procedures.
U.S. Pat. No. 5,425,644 to Szinicz for a xe2x80x9cSurgical Training Apparatus and Methodxe2x80x9d discloses an apparatus for training in surgical procedures. It includes a pump, tubing, and a fluid-containing reservoir connected to non-living animal tissue, such as organs obtained from a slaughterhouse. The fluid is preferably an approximation to xe2x80x9cthe physical properties of blood, e.g., in viscosity, density, and color. The fluid flows through the non-living animal tissue and exits to the reservoir from which it is recirculated by the pump. In one embodiment, the pump is a peristaltic flow type to provide a pulsating fluid flow. Alternatively, a fluid interrupter creates a pulsating flow. Pressure gauges may be employed to monitor and regulate the pressure of the circulating fluid.
The references mentioned above are not admitted to be prior art with respect to the present invention. The described references suffer from various limitations, which are overcome by the present invention as described below.
The present invention is a device and method for microsurgical training. Current laboratory training models, while essential for developing surgical skills, are limited in their effectiveness, especially with microvascular procedures. Training using cadavers lacks the bleeding, pulsation and fluid filling of the vascular system which is required for realistic training in vascular procedures. The alternative is to use live anesthetized animals, which do not represent true human anatomy and have ethical issues with regard to the use of live animals for surgical training.
The present invention overcomes the limitations of the prior surgical training models by using cadaveric anatomy, preferably human cadaveric anatomy for medical training and animal cadaveric anatomy for veterinary training, with filling of the vascular system by fluids under pressure to simulate the appearance and function of live surgery. Whether human or animal, it is desirable that the cadaveric anatomy be embalmed using known methods to extend its usefulness for a period of time.
This approach may be used with the whole cadaveric specimen or with a portion of cadaveric anatomy, such as the head, arm or leg, or an organ, such as the heart, liver or brain. One or more arteries on the specimen of cadaveric anatomy are cannulated and connected to an arterial reservoir containing a red colored fluid. The arterial reservoir is further connected to a pulsating machine which provides pulsating pressure to simulate the normal pulsations of the arterial system. The fluid in the reservoir is maintained at a pressure similar to that in the living subject from which the cadaveric anatomy is obtained. However, the pressure is adjustable as needed to accommodate various procedures practiced on, or conditions in, the cadaveric anatomy.
One or more veins on the specimen are also cannulated and connected to a venous reservoir of blue or dark red colored fluid. The venous reservoir is maintained at a pressure similar to that of the living subject from which the cadaveric anatomy is obtained in order to simulate vein filling but no pulsation is applied. However, the pressure in the venous reservoir may be adjusted if another pressure is desirable for a particular procedure or exercise. The venous reservoir and the arterial reservoir along with the pulsating pressure machine and ancillary equipment may be incorporated into a unitary container.
Finally, a clear fluid reservoir can be connected to the specimen. For example, in the case of the cadaveric head or other specimen of cadaveric anatomy having a spinal canal, one or more tubes may be introduced into the spinal canal and connected to the clear fluid reservoir with adjustable flow to simulate cerebrospinal fluid.
The cadaveric specimen so prepared may be used for training on various surgical procedures, including surgical approach, suturing and repair of the vessels, aneurysm clip application, catheterisation, tumor resection, cadaveric dissection, etc. The present invention may also be used in training on and testing of new medical devices, medical, veterinary and nursing school training, residency training, and anatomical studies. As used herein, the term xe2x80x9csurgical training proceduresxe2x80x9d refers to any of the procedures, training, testing or studies mentioned above.
The colored fluid used in the invention may be water that is colored with food dyes. However, in order to more fully simulate the vascular system, the colored fluid employed in the procedure may be thickened to more closely mimic the viscosity of normal blood.
The fluids that are used to fill the arteries and veins of the specimen of cadaveric anatomy do not circulate through a pump. Instead means are provided for the application of static air pressure to flexible fluid containers so that the pressure is applied indirectly to the arterial and venous systems. Likewise, the pulsating pressure for the arterial system is provided by applying pulsating air pressure to the flexible fluid containers.
These and other features, objects and advantages of the present invention will become better understood from a consideration of the following detailed description of the preferred embodiments and appended claims in conjunction with the drawings as described following: